Re: [Emc-users] Mesa 7i47S issue

[Andrew]

2017-06-20 23:35 GMT+03:00 Peter C. Wallace :

>
>> This is not unexpected, the card is probably fine
>
> The 7I47S has differential inputs, They are not designed to interface with
> single ended signals but can if needed.
>
> The only way the inputs will work reliably is to have a positive
> differential voltage across the inputs in one case and a negative
> differential voltage in the other case.
>
> If you have single ended say 5V signals you wish to read what you can do
> is this:
>
> Make a low impedance voltage reference of 2.5V with 2 series 100 Ohm
> resistors from the 7I47S 5V pins.
>
> Connect this 2.5V reference to the inverted input pin of all the 7I47S
> inputs
> you wish to use, then connect your 5V single ended signals to the
> non-inverted inputs. Now when you input signal is 5V the input pair see
> +2.5V and when input signal is 0V, The input pair see -2.5V
>
> (this will only work with termination off)
>
>
Thanks a lot! I'll try that.

Like this, right?

​
​I think I better supply 5V to P1 in this case.

What is termination in this board? Simply a resistor across the input? What
is it for?

Thanks
Andrew
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Re: [Emc-users] Mesa 7i47S issue

[Peter C. Wallace]

On Tue, 20 Jun 2017, Andrew wrote:


Date: Tue, 20 Jun 2017 22:33:43 +0300
From: Andrew <pkm...@gmail.com>
Reply-To: "Enhanced Machine Controller (EMC)"
<emc-users@lists.sourceforge.net>
To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net>
Subject: Re: [Emc-users] Mesa 7i47S issue

2017-06-17 20:15 GMT+03:00 Andrew:


2017-06-17 18:34 GMT+03:00 Danny Miller:


Similarly the inputs aren't true differential, they're an optoisolator's
input diode with a series resistor to produce the rated trigger current
when +5v is applied + to -.  Due to some esoteric details in how the bus
switch drive output works, these work best if you tie the + to +5v and use
the pin to drive the - to gnd.  The signal is weaker if you do it the other
way.



Thanks for the tip!
I was going to try the weaker way.
If there's a series resistor, it's safe to drive full 5V between /RX and
RX.
7i47s has GND and 5V pins near RX terminals, pretty handy to connect
either way.

Well today I spent a couple of hours trying to get that alarm signal to

7i47s
This was my basic idea
[image: ??  1]
This connection IIRC caused flickering LED (with termination jumper off).
I tried replacing RX and /RX wires, still nothing.

It doesn't look like there's an optocoupler input between RX and /RX...

Also I tried experimenting with RX0 input and I think something's got
broken, because now I can turn it on/off with termination jumper
left/right. Other inputs doesn't work like this.


This is not unexpected, the card is probably fine

The 7I47S has differential inputs, They are not designed to interface with 
single ended signals but can if needed.


The only way the inputs will work reliably is to have a positive differential 
voltage across the inputs in one case and a negative differential voltage in 
the other case.


If you have single ended say 5V signals you wish to read what you can do is 
this:


Make a low impedance voltage reference of 2.5V with 2 series 100 Ohm 
resistors from the 7I47S 5V pins.


Connect this 2.5V reference to the inverted input pin of all the 7I47S inputs
you wish to use, then connect your 5V single ended signals to the non-inverted 
inputs. Now when you input signal is 5V the input pair see +2.5V and when 
input signal is 0V, The input pair see -2.5V


(this will only work with termination off)




Peter Wallace
Mesa Electronics

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Re: [Emc-users] Mesa 7i47S issue

[Andrew]

2017-06-17 20:15 GMT+03:00 Andrew:

> 2017-06-17 18:34 GMT+03:00 Danny Miller:
>
>> Similarly the inputs aren't true differential, they're an optoisolator's
>> input diode with a series resistor to produce the rated trigger current
>> when +5v is applied + to -.  Due to some esoteric details in how the bus
>> switch drive output works, these work best if you tie the + to +5v and use
>> the pin to drive the - to gnd.  The signal is weaker if you do it the other
>> way.
>
>
> Thanks for the tip!
> I was going to try the weaker way.
> If there's a series resistor, it's safe to drive full 5V between /RX and
> RX.
> 7i47s has GND and 5V pins near RX terminals, pretty handy to connect
> either way.
>
> Well today I spent a couple of hours trying to get that alarm signal to
7i47s
This was my basic idea
[image: Вбудоване зображення 1]
This connection IIRC caused flickering LED (with termination jumper off).
I tried replacing RX and /RX wires, still nothing.

It doesn't look like there's an optocoupler input between RX and /RX...

Also I tried experimenting with RX0 input and I think something's got
broken, because now I can turn it on/off with termination jumper
left/right. Other inputs doesn't work like this.
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Re: [Emc-users] Mesa 7i47S issue

[Andrew]

2017-06-17 18:34 GMT+03:00 Danny Miller:

> That's not a true differential output.  It's an optoisolator's two output
> terminals.  Since they're isolated, neither terminal is tied to a gnd or +
> so you can connect it high or low.
>
> When tripped, it conducts current (supplied externally) from + to -.  It
> cannot generate its own voltage, only conduct.
>

> So all you need to do is hook it to a pin with an external pullup.  AFAIK
> all the 7i47 have a pullup to +5v.   Alarm+ to pin, Alarm- to gnd.   The
> pin will go low when the Alarm signal is active.
>

> Similarly the inputs aren't true differential, they're an optoisolator's
> input diode with a series resistor to produce the rated trigger current
> when +5v is applied + to -.  Due to some esoteric details in how the bus
> switch drive output works, these work best if you tie the + to +5v

and use the pin to drive the - to gnd.  The signal is weaker if you do it
> the other way.


Thanks for the tip!
I was going to try the weaker way.
If there's a series resistor, it's safe to drive full 5V between /RX and RX.
7i47s has GND and 5V pins near RX terminals, pretty handy to connect either
way.

Thanks,
Andrew
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Re: [Emc-users] Mesa 7i47S issue

[Danny Miller]

That's not a true differential output.  It's an optoisolator's two 
output terminals.  Since they're isolated, neither terminal is tied to a 
gnd or + so you can connect it high or low.


When tripped, it conducts current (supplied externally) from + to -.  It 
cannot generate its own voltage, only conduct.


So all you need to do is hook it to a pin with an external pullup.  
AFAIK all the 7i47 have a pullup to +5v.   Alarm+ to pin, Alarm- to 
gnd.   The pin will go low when the Alarm signal is active.


Similarly the inputs aren't true differential, they're an optoisolator's 
input diode with a series resistor to produce the rated trigger current 
when +5v is applied + to -.  Due to some esoteric details in how the bus 
switch drive output works, these work best if you tie the + to +5v and 
use the pin to drive the - to gnd.  The signal is weaker if you do it 
the other way.



Danny


On 6/17/2017 9:30 AM, Andrew wrote:

Hello,

The stepper drive has open collector alarm output.
Can I use a differential RX input on 7i47s to read it?

Thanks
Andrew
​
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Re: [Emc-users] Mesa 7i47S issue

[Andrew]

Hello,

The stepper drive has open collector alarm output.
Can I use a differential RX input on 7i47s to read it?

Thanks
Andrew
​
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Re: [Emc-users] Mesa 7i47S issue

[Andrew]

2017-04-06 22:43 GMT+03:00 Peter C. Wallace:

>
> As far as I can tell from the source the svst1_4_7i47S does put stepgen 0
> at
> TX4,TX5 Stepgen 1 at TX6,TX7, stepgen 2 at TX0,TX1 and stepgen 3 at TX2,TX3
>

Right! That's what I observed.
Err... now I see that it's in the manual, J1 pinout.. Sorry.

Another question: what is different about 7i80hd_16_svst1_4_7i47s*d*.bit ?

Thanks
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Re: [Emc-users] Mesa 7i47S issue

[Peter C. Wallace]

On Thu, 6 Apr 2017, Andrew wrote:

> Date: Thu, 6 Apr 2017 22:22:25 +0300
> From: Andrew 
> Reply-To: "Enhanced Machine Controller (EMC)"
> 
> To: "Enhanced Machine Controller (EMC)" 
> Subject: [Emc-users] Mesa 7i47S issue
> 
> Hello!
>
> I've been testing 7i80 (7i80hd_16_svst1_4_7i47s.bit) with 7i47S.
> According to the manual and hm2 load report I should have stepgen0..3 at
> TX0...TX7 outputs.
> But what I seem to have is stepgen0..1 at TX4...7, stepgen2..3 is at TX0..3.
> This is pretty confusing.
> Or am I missing something?
>
> Thanks,
> Andrew

As far as I can tell from the source the svst1_4_7i47S does put stepgen 0 at 
TX4,TX5 Stepgen 1 at TX6,TX7, stepgen 2 at TX0,TX1 and stepgen 3 at TX2,TX3


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Peter Wallace
Mesa Electronics

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